CComTearOffObject implements a tear-off interface as a separate object that is instantiated only when that interface is queried for. The tear-off is deleted when its reference count becomes zero. Typically, you build a tear-off interface for an interface that is rarely used, since using a tear-off saves a vtable pointer in all the instances of your main object.

You should derive the class implementing the tear-off from CComTearOffObjectBase and from whichever interfaces you want your tear-off object to support. CComTearOffObjectBase is templatized on the owner class and the thread model. The owner class is the class of the object for which a tear-off is being implemented. If you do not specify a thread model, the default thread model is used.

You should create a COM map for your tear-off class. When ATL instantiates the tear-off, it will create CComTearOffObject<CYourTearOffClass> or CComCachedTearOffObject<CYourTearOffClass>.

For example, in the BEEPER sample, the CBeeper2 class is the tear-off class and the CBeeper class is the owner class: